Electromagnetic transducers have been used in musical instruments for many years. When used on instruments, a transducer is commonly referred to as a pickup. Fender (U.S. Pat. No. 2,968,204) discloses a common type of pickup that is prevalent on many modern electric guitars. It consists of a several cylindrically shaped magnetic elements, commonly known as pole pieces, each having an electrically conductive coil disposed thereon. The pole pieces are linearly aligned and extend perpendicularly away from the body of a guitar. Each string of the guitar is configurable to extend through the center of adjacent pole pieces. The Fender pickup is plagued with several problems. Most notably, the linear design of the Fender pickup causes it to reproduce stray magnetic fields, thereby introducing unwanted noise into resulting signals. Isakson (U.S. Pat. No. 4,378,722) addresses this problem by introducing a series of ring-shaped pickups for receiving instrument strings therein, thereby minimizing the reproduction of stray magnetic fields. While the Isakson pickups reduce noise, they simultaneously suffer because each of the ring-shaped pickups is only weakly affected by magnetic flux. Davidson (U.S. Pat. No. 3,571,483) addresses the limitations of Isakson and Fender by using a linear pole piece that is enclosed by a yoke of opposite polarity that acts as a magnetic shield. Although Davidson offers some improvements, it suffers in that its design is overly complex, expensive, and unable to interface with standard guitars.
The Fender pickup also suffers because it is unable to separate signals from each individual magnetic element and because it reproduces signals from every plane of string vibration. These limitations result in lower quality signals and introduce difficulties in reproducing an instrument's entire range of frequencies. Isvan (U.S. Pat. No. 6,392,137), Juszkiewicz (U.S. Pat. No. 7,166,794), and Isakson teach pickup designs that reproduce signals from each magnetic element and from a single plane of string vibration. However, they each rely on the ring-shaped pickups described supra for Isakson. And, although Davidson teaches a pickup design that reproduces signals from each magnetic element, the signals are insensitive to the plane of string vibration.
Accordingly, none of the available pickup designs have been able to simultaneously provide low noise, high magnetic flux sensitivity, signal independence, and sensitivity to a single plane of string vibration. What is needed then is a novel electromagnetic transducer for instrument pickups.